Stringed instrument with sliding variably spaced frets

ABSTRACT

The invention comprises a stringed instrument of the type having an elongated neck normally provided with spaced frets and has a fret block slideably mounted on the neck with several frets thereon to replace the usual frets. The fret block includes means to move the frets longitudinally along the fret block relative to one another as a function of the position of the fret block on the neck, so that as the block slides on the neck the appropriate non-uniform spacing between frets is maintained at any position along the neck to correspond with the varied fret spacing along the neck of an ordinary stringed instrument.

United States Patent [1 1 Dunlap 1 July 15, 1975 STRINGED INSTRUMENT WITH SLIDING VARIABLY SPACED FRETS [76] Inventor: Philip A. Dunlap, 202 N. Third, El

Cajon, Calif. 92021 {22] Filed: Aug. 23, 1974 [21] App]. No.: 500,115

[52] US. Cl. 84/314 [51] Int. Cl. Gl0d 3/06 [58] Field of Search 84/314 [56] References Cited UNITED STATES PATENTS 668,060 2/1901 Shelton 84/314 X 992,765 5/1911 Garrett 84/314 1,348,894 8/1920 Rahne 84/314 2,489,657 11/1949 McBride.... 84/314 X 3,469,489 9/1969 Barth 84/314 Primary ExaminerLawrence R. Franklin Attorney, Agent, or FirmRalph S. Branscomb [57] ABSTRACT The invention comprises a stringed instrument of the type having an elongated neck normally provided with spaced frets and has a fret block slideably mounted on the neck with several frets thereon to replace the usual frets. The fret block includes means to move the frets longitudinally along the fret block relative to one another as a function of the position of the fret block on the neck, so that as the block slides on the neck the appropriate non-uniform spacing between frets is maintained at any position along the neck to correspond with the varied fret spacing along the neck of an ordinary stringed instrument.

8 Claims, 4 Drawing Figures I l l I l l l l .1

STRINGED INSTRUMENT WITH SLIDING VARIABLY SPACED FRETS BACKGROUND OF THE INVENTION When playing a conventional fretted instrument such as a guitar, the musician often wishes to slide his chording hand up and down the guitar neck to produce tones of continuously varying pitch, but when doing so, because of the nature of the fixed fret instrument, the tone often resembles a sequence of tones representing the sounds produced by fingering each of the consecutive frets. Not-fretted instruments, on the other hand, are capable of producing continually variable tones but are disadvantageous because of the extreme difficulty of depressing each string in exactly the right place when a melody or chord is being played.

SUMMARY OF THE INVENTION The present invention combines the advantages of the fixed fret instrument and the sliding tone capabilities of non-fretted instruments and comprises a stringed instrument having a non-fretted neck with a fret block slideably mounted thereon which can be moved back and forth along the neck while playing. The fret block is provided with movable frets and a mechanism which co-acts with structure of the neck of the instrument to vary the fret spacing as the fret block slides so that at any position on the neck the frets are spaced identically to the spacing of the frets on a conventional instrument.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top plan view of a portion of a guitar incorporating the sliding fret unit;

FIG. 2 is an enlarged top plan view of the fret unit with portions cut away;

FIG. 3 is a sectional view taken on line 33 of FIG. 2; and

FIG. 4 is an enlarged sectional view taken on line 44 of FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The instrument of the invention can be any of a number of stringed instruments which normally have a fretted neck, the example used being a guitar, but ukeleles, banjos and the like would also be included. These instruments commonly have a tuning board to which the strings 12 are attached by means of the adjustable tuning posts 14, the strings passing from the tuning posts through grooves in a bridge 16 and extending along the neck 18 to a second bridge, not shown, to the body 20 of the instrument to which they are anchored.

In the present invention the spaced frets which are normally mounted along the neck of the guitar are omitted and instead 21 fret block 22 is used which is provided with a plurality of movable frets 24 and a stationary fret 26 disposed on the block just beneath the strings to replace conventional frets. The fret block slides along the guitar neck and can be positioned wherever the player is fingering at any particular mo ment, and for purposes of this description and the claims the term fret block includes the entire mechanism which moves along the guitar neck.

The fret block could be any sliding element with spaced frets rigidly and immovably mounted on the front face, except for the fact that the fret spacing of most, if not all types, of instruments varies from one end of the neck to the other so that in the present invention the spacing between frets on the sliding block must vary as a function of the block position on the neck. The particular mechanism for varying fret spacing disclosed herein is intended to be exemplary only and not limiting, as clearly numerous arrangements could be provided.

In the illustrated embodiment, the neck is provided along its entire length with a plate 28 having opposed parallel tracks 30 and two grooves 32 which extend longitudinally along the plate, diverging in the direction of the guitar body. The fret block includes a planar fingering panel 34 having depending L-shaped lips 35 which are captured between the tracks 30 so that the panel freely slides along the length of the neck.

Immediately below the fingering panel are four fret plates 36 which are free to slide relative to the fingering panel, and a fixed fret plate 38 which is immovably secured to the underside of the panel 34 as shown. Each of the movable fret plates has mounted to the ends thereof one of the frets 24, which are secured to the plate by legs 40 which extend through longitudinal slots 42 in the fingering panel so that the spanner portions of the frets lie above the panel either in slightly spaced relation thereto or lightly touching the surface. The stationary fret 26 is mounted to the fingering panel above the stationary plate 38.

As best illustrated in FIG. 2, the three central plates are substantially diamond shaped with the end plates being half diamonds, and the pointed edges of the diamonds further having diamond-shaped relieved portions 43 in the top and bottom sides alternatively so that the plates may nest together to some extent as shown by dashed lines in FIG. 2.

The fret plates are biased together by springs 44 such that they are all drawn toward the fixed plate 38. Between each of the plates is a pair of spacer elements whose lower ends freely track in the grooves 32 and whose upper portions are imperfect trapezoids which space the plates apart. A bar 48 may be secured under one end of the panel as shown for reinforcement.

The operation of the fret block should be fairly clear from the description of its structure. As the block slides to the right in the drawings, the spacer pairs 46 which track in the diverging grooves 32 expand outwardly, permitting the plates 36 to slide together under tension from the springs 44 so that the frets converge. Displacement of the fret block to the left of course produces the opposite effect.

Clearly if the edges of the plates are triangular as shown and the diverging grooves 32 are straight, the change in fret spacing will be a linear function of the position of the fret block on the neck. This may not be desirable, inasmuch as the fret spacing on some instruments does not vary linearly. Any non-linear arrangement may be provided very simply by cutting the grooves 32 so that they reflect the function which the fret spacing is to follow. The edges of the fret plates could also be made non-linear with the same result, although it would probably be desireable in this situation to make the spacers 46 rounded at their plateeontaeting edges, or even circular or semi-circular.

The stationary fret 26 is spaced from the end of the fret block 22 such that when the fret block contacts the tuning board first fret spacing will be proper. At the other end of the neck, since the frets contract away from the body on the fret board, a non-fretted length of the block will separate the closest fret from the body. This may require construction of a slightly longer neck than on conventional instruments. Alternatively the block could be reversed, with the stationary fret striking the highest note. The fret block could be provided with a rigid shroud extending from the edges of the fingering plate 34 around the neck so that the musicians chording hand would not bear on the stationary edges of the neck.

There are two crucial elements in the invention which may be varied considerably without eliminating the advantages of the instrument. First, the guitar neck must be provided with some type of structural feature along its neck which varies along the neck, and second, a sliding member of some type must be provided having movable frets and means coacting with the neck structure to vary fret spacing as a function of the position on the neck. The neck structure could be a single diagonal groove, or a groove or rib that diverges toward one end. Many variations of the disclosed sliding block apparatus could be made within the scope of the invention, as various linear and nonlinear expansion mechanisms are well known in the engineering art. The novelty of the invention resides primarily in the combination of such a mechanism with a stringed musical instrument generally as described herein.

I claim:

l. A stringed musical instrument having an elongated neck and a plurality of generally parallel strings spaced from said neck and extending along the longitudinal direction of said neck;

a block mounted on said neck to slide in said longitudinal direction along said neck, said block having a plurality of frets mounted thereon transversely of said longitudinal direction and movable relative to said block in longitudinal direction;

means responsive to movement of said block along said neck to vary the spacing between said frets as a function of the position of said block on said neck.

2. Structure according to claim 1 and including a fret immovably fixed to said mounting block.

3. Structure according to claim 2 wherein the number of movable frets is four whereby, in conjunction with said immovable fret five frets, are provided to accommodate the normal span of the hand when chord- 4. A stringed musical instrument as in claim 1 wherein said neck is attached to an instrument body on one end and a tuning board on the other end, and said means comprises coacting block means and neck structure, said neck structure spanning the substantial length of said neck and consecutive portions of said structure being varied according to the positions thereof on said neck to coact with said block means for increasing the fret spacing as said block approaches the tuning board and decreasing said spacing as said block approaches said body.

5. Structure according to claim 4 wherein said structure on said neck comprises two longitudinally extended divergent grooves and said block means includes a plurality of spacer pairs tracking in said grooves, and each of said movable frets is mounted on a sliding plate having angled edges and being alternately disposed on said neck with said spacer pairs and bearing on the latter, such that convergence of the individual spacers in each pair causes the separation of adjaccnt plates.

6. Structure according to claim 5 and including means to bias said plates together.

7. Structure according to claim 5 wherein said block includes a panel mounted between said plates and said frets, said panel having longitudinal slots therein and said frets are mounted to said plates through said slots.

8. Structure according to claim 7 wherein said neck has a pair of longitudinal tracks engaging the opposing edges of said panel in slidably mounted relationship on said neck. 

1. A stringed musical instrument having an elongated neck and a plurality of generally parallel strings spaced from said neck and extending along the longitudinal direction of said neck; a block mounted on said neck to slide in said longitudinal direction along said neck, said block having a plurality of frets mounted thereon transversely of said longitudinal direction and movable relative to said block in longitudinal direction; means responsive to movement of said block along said neck to vary the spacing between said frets as a function of the position of said block on said neck.
 2. Structure according to claim 1 and including a fret immovably fixed to said mounting block.
 3. Structure according to claim 2 wherein the number of movable frets is four whereby, in conjunction with said immovable fret five frets, are provided to accommodate the normal span of the hand when chording.
 4. A stringed musical instrument as in claim 1 wherein said neck is attached to an instrument body on one end and a tuning board on the other end, and said means comprises coacting block means and neck structure, said neck structure spanning the substantial length of said neck and consecutive portions of said structure being varied according to the positions thereof on said neck to coact with said block means for increasing the fret spacing as said block approaches the tuning board and decreasing said spacing as said block approaches said body.
 5. Structure according to claim 4 wherein said structure on said neck comprises two longitudinally extended divergent grooves and said block means includes a plurality of spacer pairs tracking in said grooves, and each of said movable frets is mounted on a sliding plate having angled edges and being alternately disposed on said neck with said spacer pairs and bearing on the latter, such that convergence of the individual spacers in each pair causes the separation of adjacent plates.
 6. Structure according to claim 5 and including means to bias said plates together.
 7. Structure according to claim 5 wherein said block includes a panel mounted between said plates and said frets, said panel having longitudinal slots therein and said frets are mounted to said plates through said slots.
 8. Structure according to claim 7 wherein said neck has a pair of longitudinal tracks engaging the opposing edges of said panel in slidably mounted relationship on said neck. 